If I use Hextech Ray on a 5-Might unit (dealing 3 damage) and then use Smoke Screen on it (reducing it to 1 Might), does it die?

Ruling: Yes, the unit dies. A unit dies when it has damage marked on it equal to or greater than its current Might.

Sequence:

• Hextech Ray deals 3 damage to the 5-Might unit
• Smoke Screen reduces the unit to 1 Might
• The unit now has 3 damage marked on it and 1 Might, so it dies

Nuances:

• Damage is tracked as "damage marked on a unit" rather than as remaining HP
• The unit must have non-zero damage for this rule to apply (a unit with 0 damage and 0 Might does not die)